In the construction of machines and vehicles, but also in other technical fields, it is desirable to preassemble subassemblies and to put them together to form a finished product. It is therefore customary already to provide components at the preassembly stage with fastening elements, such as screws or bolts, with which the components are fastened to other subassemblies at the completion stage. The fastening elements have to be attached to the components in the position required for the subsequent final assembly and secured in such a manner that they do not change this position even during transportation.
It is thus known in practice in the construction of vehicles to preassemble contact bridges for steering wheels. Contact bridges are necessary for actuating the horn. The complete contact bridge comprises a contact plate and a further sheet-metal part which is arranged at a distance from the said plate and is referred to as a contact bridge. The two parts are provided at at least one point with contacts. Compression springs are arranged between the two parts and ensure that they keep a minimum distance apart, so that contacts lying opposite one another do not come into contact. The contacts are made by pressing down the contact bridge in the direction of the contact plate.
The contact bridge and the contact plate are connected to each other via screws. The screws are introduced from the upper side of the contact bridge through corresponding apertures and, with the compression springs being positioned in between, are inserted through the contact plate, so that the thread is exposed. The fastening takes place by means of a toothed disc in each case. A tool is used to press the toothed disc into a recess in the screw. A connection between the screw and the contact plate is therefore produced and the distance between the latter and the contact bridge is ensured. A complete subassembly is therefore provided. The screws for fastening the complete subassembly to the steering wheel are securely fastened at one end and at the other end are guided rotatably in the bushings.
The disadvantage of this arrangement is that the toothed disc for fastening the screw to the contact plate is required as an additional component and that the apertures for the screws have to be encapsulated with plastic in a separate injection mould, so that a plastic bushing for guiding the screws is produced.